376 Miscellaneous, . 



its point directed downwards, and completely resembling in its aspect 

 the interspinous bones which sustain the rays of the fins. It is of 

 the same nature as these. 



b. The rays are represented by two small osseous rods, laid trans- 

 versely in a horizontal plane, and articulated by their base, at the 

 level of the median line, with the corresponding interspinous bone. 

 Each of these rods, taken by itself, represents one-half of a fin-ray ; 

 this half, instead of remaining united with its opposite half in a 

 vertical plane, has departed from it to fall down on the side. 



c. The articular ossicle is an unpaired symmetrical bone, extended 

 across the disk, of which it occupies the whole width. It consists 

 of a very narrow median portion and of two lateral portions, which 

 are widened into lamince or quadrilateral palettes. From the upper 

 surface of the latter springs a small lamellar apophysis directed 

 backwards (articular apophysis), beneath which the extremity of the 

 ray belonging to the same segment is attached. 



This ossicle, the nature of which has hitherto been misunderstood, 

 must, in my opinion, be regarded as the equivalent of the little 

 osseous nodule which occurs in the fin in the space left between the 

 bases of the two halves of a ray. 



As regards the mechanism by means of which the fixation of the 

 disk is effected, this is easy to understand when we have ascertained 

 the arrangement of the pieces of this little apparatus. 



Each ray, in fact, serves as a support to a lamina of the disk. It 

 is capable of moving upon its anterior border as upon a hinge, and 

 consequently of inclining the lamina with which it corresponds either 

 forwards or backwards. This double movement is effected by means 

 of small muscles inserted, on the one hand, upon an apophysis of the 

 base of the rays projecting at the lower surface of the disk, and, on 

 the other, upon the interspinous bones of the neighbouring segments. 

 These bundles correspond with the elevator and depressor muscles of 

 the rays of fins. 



It is easy to demonstrate, by means of a very simple geometrical 

 construction, that when the lamellae of the disk are raised, the space 

 which they intercept is enlarged ; the air consequently tends to be- 

 come rarefied in this space, and, as all communication with the ex- 

 terior is interrupted by the cutaneous fold which borders the disk, 

 an effect of suction is thus produced, exactly comparable to that of 

 the cupping-glass. — Comptes Rendus, March 18, 186/, pp. G25-fi27. 



Apus and Branchipus. 



Mr. Grunow has lately discovered at Pottenstein, near Vienna, a 

 locality of Apus cancriformis and of Branchipus stapialis, the two 

 Ph}llopoda remarkable for their affinity with the extinct HymenO' 

 carts, Ceratincaris, Dithyrocaris, and Limuloid Crustaceans. The 

 Apus and Branchipus under notice live in a pool about 20 feet broad 

 and 30 feet long, which is completely dried up in summers that are 

 hot throughout. In September 1866 myriads were observed in the 

 slimy water of the pool.— /w^). Geol. Instit. Vienna. Feb. 19, 1867. 



